HTML code is adding double spacing

I use this same HTML code and CSS for my wordpress posts and it works just fine. Now I'm trying to use it on a forum post and it adds double spacing, making it look like this: http://imgur.com/5dm8213
When it should look like this: http://imgur.com/TbU9SJD

What can I do to remove all the extra spacing?

This is the HTML I'm using for this example, which is based off my CSS template underneath it: